With the fast development of broadband networks and particularly the emergence of new services based on the broadband networks, the bandwidth required on a network in the future will increase sharply. Applications of Internet Protocol (IP) telephony, the 3rd Generation (3G) services, video conference, Video on Demand (VoD) and many emerging Point to Point (P2P) services are rapidly consuming the remaining bandwidths in the bearer network.
Clustering is a most effective technology that solves the issues of scalability. Introduction of clustering into router structuring intends to connect two or more common core routers in such a way that the core routers can collaborate and perform parallel processing so that the capacity of a system is expanded smoothly. To the outside, the clustered routers are one logical router. Parallel Packet Switching (PPS) cascades multiple independent switch fabrics to create a multi-stage multi-plane switching matrix so as to break the restrictions in switching capacity, power consumption and heat dissipation in the case of a single switching chassis and implement a larger-capacity routing and switching system.
At present, when routers and other communication devices are expanded through inter-chassis cascade, a central switching chassis is generally placed to realize data switching between line processing chassis. The central switching chassis is generally implemented in a multi-plane switching structure.
FIG. 1 shows a first solution in the prior art which includes four T line processing chassis (routing nodes). Each T line processing chassis has five independent Ts switch fabric units, numbered from 0 to 4. The TX switching chassis (TX-Matrix platform) also includes five independent Ts switch fabric units, numbered from 0 to 4. The Ts units are connected on a one-to-one basis to compose five independent switching planes. Each switching plane is distributed in one TX switching chassis and four T line processing chassis. It should be noted that FIG. 1 only shows two T chassis and the other two T chassis are connected to the TX switching chassis in the same way as the shown two T line processing chassis are connected to the TX chassis. An external network is connected to the Ingress Packet Forwarding Engine (Ingress PFE) via a Physical Interface Card (PIC) and packets therefrom are distributed to different switching planes by information sources after being processed by the Ingress PFE.
During the process of implementing the present invention, the inventor finds that the above solution does not provide good scalability in practice. In particular, each stage-2 Ts switch fabric unit in the TX switching chassis has only four interfaces and therefore can only be cascaded with four T line processing chassis. To connect more T chassis, the entire TX chassis needs to be replaced. In addition, because the above router cluster includes only one TX switching chassis, once the TX chassis fails, data services on the four T line processing chassis in connection with the TX chassis will all be interrupted. Therefore, the reliability of the router cluster is low.
FIG. 2 shows the structure of a router cluster composed by means of multi-chassis cascade with 9 line processing chassis according to a second solution in the prior art. The router cluster includes eight switching planes which share loads evenly. Inside each switching chassis is a stage-3 switch fabric. Physically, the stage-1/3 switch fabric unit Ts1,3 of each switching plane is placed in the T line processing chassis and the stage-2 switch fabric unit Ts2 is placed in the central switching chassis TX. Between stage 1 and stage 2 and between stage 2 and stage 3, an inter-chassis cascade optical cable is connected. The T line processing chassis consists of a Ts2 switch fabric unit, a Tb electrical backplane and several T1 line processing units.
Unlike the first solution, the second solution includes a TXa optical cross-connect unit placed between Ts1,3 and Ts2 of each switching plane. The TXa unit rearranges the cascade fibers between TX and T and afterwards connects the fibers to the Ts2 in the TX switching chassis. With the TXa, fibers can be regrouped so that the TX can connect more T chassis without the need to replace the Ts2. Thus, the router cluster is upgraded.
In the second solution, each TXa unit corresponds to one stage-2 switch fabric unit Ts1,3. Each TXa has nine optical interfaces, each connecting one T line processing chassis. One TXa is bound with one Ts2 and can provide nine optical interfaces to implement switching between nine T line processing chassis. The entire 9-chassis cascade system needs eight such binding units.
As shown in FIG. 3, when the above router cluster is scaled up to a cascade of 18 T line processing chassis, the TXa that has nine optical interfaces in the TX switching chassis needs to be replaced by a TXa that has at least 18 optical interfaces and each 10-port TXa is bound respectively with two Ts2 switch fabric units to compose a binding unit. Each binding unit provides 18 optical interfaces and implements data switching between 18 T line processing chassis. The binding unit connects 18 T chassis in cascade in a same structure as shown in FIG. 2. The 18-chassis cascade system requires eight such binding units. In comparison with the 9-chassis cascade system, the switching capacity of each binding unit is doubled.
As described above, when it is necessary to further expand the capacity of the router cluster, the 18-port TXa needs to be replaced with a 36-port TXa and each TXa is bound respectively with four Ts2 units so as to implement data switching between the TX and 36 T line processing chassis.
Although the second solution allows capacity expansion of the router cluster, the optical cross-connect unit in the switching chassis needs to be replaced. Because the cost of an optical cross-connect unit is high, this will result in the waste of user investment.